Tertiary lock system power unit

ABSTRACT

A system for moving an aircraft thrust reverser component includes a power drive unit, a thrust reverser actuator assembly, and a tertiary lock system. The power drive unit is operable to rotate and supply a rotational drive force. The thrust reverser actuator assembly receives the rotational drive force from the power drive unit and moves the thrust reverser component between a stowed position and a deployed position. The tertiary lock system selectively engages and disengages the thrust reverser component and includes a tertiary lock power unit, an electromechanical tertiary lock assembly, and a voltage limiting circuit. The voltage limiting circuit limits the voltage magnitude of a control signal supplied to the tertiary lock assembly to a predetermined value.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 10/990,918, filed Nov. 16, 2004, now U.S. Pat. No. 7,409,820.

TECHNICAL FIELD

The present invention relates to aircraft engine thrust reverseractuation systems and, more particularly, to an electrically-operatedthrust reverser system tertiary lock that includes a voltage limitingcircuit.

BACKGROUND

When a jet-powered aircraft lands, the landing gear brakes andaerodynamic drag (e.g., flaps, spoilers, etc.) of the aircraft may not,in certain situations, be sufficient to slow the aircraft down in therequired amount of runway distance. Thus, jet engines on most aircraftinclude thrust reversers to enhance the braking of the aircraft. Whendeployed, a thrust reverser redirects the rearward thrust of the jetengine to a generally or partially forward direction to decelerate theaircraft. Because at least some of the jet thrust is directed forward,the jet thrust also slows down the aircraft upon landing.

Various thrust reverser designs are commonly known, and the particulardesign utilized depends, at least in part, on the engine manufacturer,the engine configuration, and the propulsion technology being used.Thrust reverser designs used most prominently with jet engines fall intothree general categories: (1) cascade-type thrust reversers; (2)target-type thrust reversers; and (3) pivot door thrust reversers. Eachof these designs employs a different type of moveable thrust reversercomponent to change the direction of the jet thrust.

Cascade-type thrust reversers are normally used on high-bypass ratio jetengines. This type of thrust reverser is located on the circumference ofthe engine's midsection and, when deployed, exposes and redirects airflow through a plurality of cascade vanes. The moveable thrust reversercomponents in the cascade design includes several translating sleeves orcowls (“transcowls”) that are deployed to expose the cascade vanes.

Target-type reversers, also referred to as clamshell reversers, aretypically used with low-bypass ratio jet engines. Target-type thrustreversers use two doors as the moveable thrust reverser components toblock the entire jet thrust coming from the rear of the engine. Thesedoors are mounted on the aft portion of the engine and may form the rearpart of the engine nacelle.

Pivot door thrust reversers may utilize four doors on the engine nacelleas the moveable thrust reverser components. In the deployed position,these doors extend outwardly from the nacelle to redirect the jetthrust.

The moveable thrust reverser components in each of the above-describeddesigns are moved between the stowed and deployed positions byactuators. Power to drive the actuators may come from a dual outputpower drive unit (PDU), which may be electrically, hydraulically, orpneumatically operated, depending on the system design. A drive trainthat includes one or more drive mechanisms, such as flexible rotatingshafts, may interconnect the actuators and the PDU to transmit the PDU'sdrive force to the moveable thrust reverser components.

The primary use of thrust reversers is, as noted above, to enhance thebraking of the aircraft, thereby shortening the stopping distance duringlanding. Hence, thrust reversers are usually deployed during the landingprocess to slow the aircraft. Thereafter, when the thrust reversers areno longer needed, they are returned to their original, or stowed,position. Once in the stowed position, one or more locks are engaged toprevent unintended movement of the thrust reversers and/or actuatorsthat move the thrust reversers.

Although the number of locks may vary, many thrust reverser systemsinclude primary, secondary, and tertiary locks. Depending on thrustreverser system configuration, one or more primary locks may be coupledto one or more of the actuators, one or more secondary locks (or“brakes”) may be coupled to the PDU, and one or more tertiary locks maybe coupled to one or more of the thrust reversers.

In some thrust reverser systems, the tertiary locks may beelectromechanical type of locks that receive AC electrical power fromthe aircraft power system. The AC electrical power from the aircraftpower system, which is typically around a nominal value of 115 VAC, maybe converted to a DC power signal having a much lower voltage magnitude.This DC power signal is in turn used to control the tertiary locks. Theaircraft power system may fluctuate, both above and below, the nominalvoltage magnitude, which may cause the DC power signal supplied to thetertiary locks to also fluctuate above and below a nominal magnitude. Ifthe DC power signal fluctuates too high above the nominal magnitude, oneor more components of the tertiary locks can overheat and/or otherwisebe damaged.

Hence, there is a need for a tertiary lock system that can accommodatevoltage fluctuations in an aircraft power system while supplying DCpower to a tertiary lock in a manner that does not result in one or morecomponents of the tertiary locks overheating and/or otherwise becomingdamaged. The present invention addresses at least this need.

BRIEF SUMMARY

In one embodiment, and by way of example only, a tertiary lock systempower unit for supplying a DC tertiary lock control signal to anelectromechanical tertiary lock assembly includes a step-downtransformer, a rectifier, and a voltage limiting circuit. The step-downtransformer is adapted to receive a tertiary lock release commandsignal, which is an AC signal of a first peak voltage magnitude, and isoperable, upon receipt thereof, to supply an AC signal of a second peakvoltage magnitude that is less than the first peak voltage magnitude.The rectifier circuit is coupled to receive the AC signal of the secondpeak voltage magnitude from the step-down transformer and is configured,upon receipt thereof, to supply a DC signal of a third voltagemagnitude. The voltage limiting circuit is coupled to receive the DCsignal of the third voltage magnitude from the rectifier circuit and isoperable, upon receipt thereof, to supply the DC tertiary lock controlsignal to the electromechanical tertiary lock assembly at a fourthvoltage magnitude, which is less than or equal to a predeterminedvoltage limit.

Other independent features and advantages of the preferred tertiary locksystem will become apparent from the following detailed description,taken in conjunction with the accompanying drawings which illustrate, byway of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of portions of an aircraft jet engine fancase;

FIG. 2 is a simplified end view of a thrust reverser actuation systemaccording to an exemplary embodiment of the present invention;

FIG. 3 is functional block diagram of an embodiment of a tertiary locksystem that may be included in the thrust reverser actuation system ofFIG. 2; and

FIG. 4 is a schematic diagram of a voltage limiting circuit according toan embodiment of the present invention that may be used in the tertiarylock system of FIG. 3.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Before proceeding with the detailed description, it is to be appreciatedthat the described embodiment is not limited to use in conjunction witha specific thrust reverser system design. Thus, although the descriptionis explicitly directed toward an embodiment that is implemented in acascade-type thrust reverser system, in which transcowls are used as themoveable thrust reverser component, it should be appreciated that it canbe implemented in other thrust reverser actuation system designs,including those described above and those known now or hereafter in theart.

Turning now to the description, and with reference first to FIG. 1, aperspective view of portions of an aircraft jet engine fan case 100 thatincorporates a cascade-type thrust reverser is depicted. The engine fancase 100 includes a pair of semi-circular transcowls 102 and 104 thatare positioned circumferentially on the outside of the fan case 100. Thetranscowls 102 and 104 cover a plurality of non-illustrated cascadevanes. A mechanical link 202 (see FIG. 2), such as a pin or latch, maycouple the transcowls 102 and 104 together to maintain the transcowls102 and 104 in correct alignment on non-illustrated guides on which thetranscowls 102 and 104 translate. When the thrust reversers arecommanded to deploy, the transcowls 102 and 104 are translated aft.This, among other things, exposes the cascade vanes, and causes at leasta portion of the air flowing through the engine fan case 100 to beredirected, at least partially, in a forward direction. Thisre-direction of air flow in a forward direction creates a reversethrust, and thus works to slow the airplane.

The transcowls 102 and 104 are moved between the deploy and stowpositions via a thrust reverser control system. An exemplary embodimentof a thrust reverser control system 200 is depicted in FIG. 2, andincludes a plurality of actuators 210, which are individually coupled tothe transcowls 102 and 104. In the depicted embodiment, half of theactuators 210 are coupled to one of the transcowls 102, and the otherhalf are coupled to another transcowl 104. It is noted that theactuators 210 may be any one of numerous actuator designs presentlyknown in the art or hereafter designed. However, in this embodiment theactuators 210 are ballscrew actuators. It is additionally noted that thenumber and arrangement of actuators 210 is not limited to what isdepicted in FIG. 2, but could include other numbers of actuators 210 aswell. The number and arrangement of actuators 210 is selected to meetthe specific design requirements of the system.

The actuators 210 are interconnected via a plurality of drive mechanisms212, each of which, in the particular depicted embodiment, is a flexibleshaft. Using flexible shafts 212 in this configuration ensures that theactuators 210 and the transcowls 102 and 104, when unlocked, move in asubstantially synchronized manner. For example, when one transcowl 102is moved, the other transcowl 104 is moved a like distance atsubstantially the same time. Other synchronization mechanisms that maybe used include electrical synchronization or open loop synchronization,or any other mechanism or design that transfers power between theactuators 210.

A power drive unit (PDU) 220 is coupled to the actuators 210 via one ormore of the flexible shafts 212. In the depicted embodiment, the PDU 220includes a motor 214 that is coupled to two of the flexible shafts 212.The motor 214 may be any one of numerous types of motors such as, forexample, an electric (including any one of the various DC or AC motordesigns known in the art), a hydraulic, or a pneumatic motor. In thedepicted arrangement, the rotation of the PDU 220 results in thesynchronous operation of the actuators 210, via the flexible shafts 212,thereby causing the transcowls 102 and 104 to move at substantially thesame rate.

A control circuit 218 controls the PDU 220, and receives various signalsfrom one or more positions sensors. The control circuit 218 receivescommands from an engine control system 222 such as, for example, a FADEC(full authority digital engine control) system, and provides appropriateactivation signals to the PDU 220 in response to the received commands.In turn, the PDU 220 supplies a drive force to the actuators 210 via theflexible shafts 212. As a result, the actuators 210 cause the transcowls102 and 104 to translate between the stowed and deployed positions.

The thrust reverser control system 200 additionally includes a pluralityof locks that together function to prevent unintended movement of thetranscowls 102 and 104 from the stowed position. In the depictedembodiment, the thrust reverser control system 200 includes two primarylocks 224, a PDU lock 226 (or “brake”), and tertiary lock 228. Theprimary locks 224 are each mounted on one of the actuators 210 and areconfigured to selectively prevent movement of one of the actuators 210,and thereby prevent transcowl movement. The PDU brake 226 is configuredto selectively prevent or allow rotation of the PDU 220, and therebyprevent transcowl movement. The tertiary lock 228 is mounted on theengine nacelle (not illustrated) and is configured to selectively engagea portion of one of the transcowls 104 directly. Because the transcowls102, 104 are coupled via the mechanical link 202, the tertiary lock 228prevents movement of both transcowls 102, 104. In the depictedembodiment, the primary lock 224 and PDU brake 228 are each controlledvia the control circuit 218. However, as will be described in moredetail further below, the tertiary lock 228 forms part of a separatetertiary lock system 250, and is controlled via a separate tertiary lockpower unit 232.

It will be appreciated that the number of locks 224, 226, 228 depictedand described herein is merely exemplary of one particular embodiment,and that other numbers of locks could be used to meet specific designrequirements. It will additionally be appreciated that each of the locks224, 226, 228 is configured to default to a normally locked position by,for example, a biasing spring. Thus, when not commanded to move to theunlocked position, each lock 224, 226, 228 will be in, or move to, thelocked position. The specific structural configuration of the primarylocks 224 and PDU brake 226 is not necessary to understand or enable thepresent invention, and will therefore not be provided. However, withreference now to FIGS. 3 and 4, a more detailed description of thetertiary lock system 250 and its operation will be provided.

Turning first to FIG. 3, it is seen that the tertiary lock system 250includes two sub-systems, the tertiary lock system power unit 232 andthe tertiary lock 228. The tertiary lock system power unit 232 iscoupled to receive a single-phase, AC tertiary lock release commandsignal from, for example, the aircraft electrical power distributionsystem 302. As was previously mentioned, the frequency and voltagemagnitude of the aircraft electrical power distribution system 302 mayvary, both above and below, nominal values. As will be described in moredetail further below, the tertiary lock system power unit 232 isconfigured to convert the AC lock release command signal, which may varyin both frequency and voltage magnitude, to a DC tertiary lock controlsignal having a voltage magnitude that is limited to a predeterminedvalue. The DC tertiary lock control signal is in turn supplied to thetertiary lock 228, an embodiment of which will now be described.

The tertiary lock 228 is an electromechanical lock assembly and includesa lock 304, a DC motor 306, and a lock actuator 308. The lock 304includes a retaining member 312, locking member 314, a locking memberspring 316, and a blocking member 318, and a blocking member spring 322.The retaining member 312 is mounted on the transcowl 104 (not shown inFIG. 3), and the locking member 314 is mounted on a beam within theengine case (not shown in FIG. 3). The locking member 314 is movablebetween a locked position, in which it engages the retaining member 312,and an unlocked position, in which it disengages the retaining member312. The locking member spring 316 biases the locking member 314 towardthe unlocked position. As shown in FIG. 3, the locking member 314preferably includes a cam surface 313 that the retaining member 312engages when the transcowl 104 is returning to the stowed position. Whenthe retaining member 312 engages the cam surface 313, it moves thelocking member 314, against the force of the locking member spring 316,back into the locked position, where it is retained by the blockingmember 318.

The blocking member 318 is pivotally mounted in the engine case (asshown by double-headed arrow 315) and is configured to pivot between anengage position and a release position. The blocking member spring 322biases the blocking member 318 toward the engage position. In the engageposition, the blocking member 318 prevents the locking member 314 frommoving out of the locked position, but allows the locking member 314 tomove into the locked position from the unlocked position. In thedisengage position, the blocking member 318 allows the locking member314 to move, under the force of the locking member spring 316, to theunlocked position, or to move freely from the unlocked position to thelocked position, if engaged by the retaining member 312 as the transcowl104 moves to the stowed position.

The blocking member 318 is pivoted to the disengage position by theactuator 308, which moves in response to a drive force supplied from theDC motor 306. The DC motor 306 may be implemented as any one of numeroustypes of DC motors now known or developed in the future, but in thepreferred embodiment it is implemented as a brush-type DC motor. In anycase, the DC motor 306, in response to the DC tertiary lock controlsignal supplied by the tertiary lock system power unit 232, rotates inthe appropriate direction and supplies a drive force to the actuator308. In turn, the actuator 308 engages the blocking member 318 and movesit, against the bias force of the blocking member spring 322, to thedisengage position, thereby allowing the locking member 314 to move tothe unlocked position. It will be appreciated that when the DC tertiarylock control signal is removed, thereby de-energizing the DC motor 306,the bias force of the blocking member spring 322 moves the blockingmember 318 back to the engage position.

Turning now to a more detailed description of the tertiary lock systempower unit 232, it is seen that it includes a power unit 324 and avoltage limiting circuit 326. The power unit 324 includes a filtercircuit 328, a step-down transformer 332, and a rectifier circuit 334.The filter circuit 328 removes any unwanted high-frequency signalcomponents from the AC tertiary lock release command signal. Suchhigh-frequency signal components may be due, for example, toelectromagnetic interference (EMI). The filtered AC tertiary lockrelease command signal is then supplied to the step-down transformer332.

The step-down transformer 332 functions to reduce the voltage magnitudeof the filtered AC tertiary lock release command signal, and therectifier circuit 334, which is preferably implemented as a full-waverectifier circuit, converts the reduced magnitude AC signal to a DC lockrelease command signal. The amount that the step-down transformer 332reduces the voltage magnitude will depend, as is generally known, on theturns-ratio of the step-down transformer 332. Moreover, as waspreviously mentioned, the AC tertiary lock signal may vary in voltagemagnitude and frequency. Thus, a step-down transformer 332 with thedesired turns-ratio, as well as the desired frequency response and powerrequirements, is chosen. For example, in a particular physicalimplementation, it is postulated that the peak voltage magnitude of theAC tertiary lock release command may vary from a low value (VAC_(LOW))to a high value (VAC_(HIGH)), and the frequency may vary from a lowfrequency value (FREQ_(LOW)) to a high frequency value (FREQ_(HIGH)).Thus, the step-down transformer 326 is chosen so that, followingrectification in the rectifier circuit 334, the DC lock release commandsignal will not drop below a desired minimum value (VDC_(LOW)) when theAC tertiary lock release command signal is at the low value (VAC_(LOW))and at any frequency between the low (FREQ_(LOW)) and high (FREQ_(HIGH))frequency values.

The DC lock release command signal is supplied to the voltage limitingcircuit 326. The voltage limiting circuit 326 is configured, uponreceipt of the DC lock release command signal, to supply a DC tertiarylock control signal to the DC motor 306 that has a voltage magnitudelimited to a predetermined value (VDC_(MAX)). More particularly, whenthe voltage magnitude (VDC_(RELEASE)) of the DC lock release commandsignal is at or below the predetermined value (e.g.,VDC_(RELEASE)≦VDC_(MAX)), the DC tertiary lock control signal suppliedby the voltage limiting circuit 326 will have a voltage magnitude(VDC_(CONTROL)) equal to the DC lock release command signal (e.g.,VDC_(CONTROL)=VDC_(RELEASE)). However, if the voltage magnitude(VDC_(RELEASE)) of the DC lock release command signal exceeds thepredetermined value (e.g., VDC_(RELEASE)>VDC_(MAX)), then the DCtertiary lock control signal supplied by the voltage limiting circuit326 will have a voltage magnitude equal to the predetermined value(e.g., VDC_(CONTROL)=VDC_(MAX)). A particular preferred physicalimplementation of the voltage limiting circuit 326 is illustrated inFIG. 4, and will now be described in more detail.

As FIG. 4 shows, the voltage limiting circuit includes a voltage limitercircuit 402 and an amplifier circuit 404. The voltage limiter circuit402 functions to limit the magnitude of the DC tertiary lock controlsignal to the predetermined value, and in the depicted embodimentincludes a zener diode 406, a current limiting resistor 408, and a diode412. As is generally known, the zener diode 406 will conduct when thevoltage magnitude across it (e.g., VDC_(RELEASE)) is at or above itsso-called “zener voltage.” Moreover, once the zener diode 406 doesconduct, the voltage drop across it will be a substantially constantvalue (e.g., VDC_(MAX)). The current limiting resistor 408 is includedto limit the current flow through the zener diode 406, and the diode 412prevents reverse current flow through the zener diode 406, which couldoccur since the DC motor 306 is an inductive load.

The amplifier circuit 404 is a relatively simple, unity gain amplifierthat includes an input terminal 414, an output terminal 416, and acontrol terminal 418. The amplifier input 414 and output 416 terminalsare electrically coupled in series between the power unit 324 and the DCmotor 306, and the control terminal 418 is electrically coupled betweenthe zener diode 406 and the current limiting resistor 408. Although anyone of numerous unity gain amplifier circuit configurations could beused to implement the amplifier circuit 404, in the depicted embodimentit is implemented in a conventional Darlington amplifier configuration.As is generally known, Darlington amplifiers operate over a widetemperature range.

With the above described circuit configuration, the output of theamplifier circuit 404, which is also the DC tertiary lock controlsignal, will have a voltage magnitude substantially equal to the voltagesupplied to the amplifier control terminal 418. Thus, when the voltagemagnitude of the DC lock release command signal is below the zenervoltage, no current will flow through the zener diode 406, and thisvoltage magnitude will be supplied to the amplifier control terminal418. As a result, the voltage magnitude of the DC tertiary controlsignal will be substantially equal to that of the DC lock releasecommand signal. Conversely, when the voltage magnitude of the DC lockrelease command signal is at or above the zener voltage, current willflow through the zener diode 406, and the zener voltage magnitude(VDC_(MAX)) will be supplied to the amplifier control terminal 418. As aresult, the voltage magnitude of the DC tertiary control signal will besubstantially equal to the zener voltage magnitude.

The tertiary lock system described herein can accommodate voltagefluctuations in an aircraft power system while supplying DC power to atertiary lock, and do so in a manner that does not result in one or morecomponents of the tertiary locks overheating and/or otherwise becomingdamaged. The system includes a voltage limiting circuit that isrelatively simple, and relatively inexpensive, to implement.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt to a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe appended claims.

1. A tertiary lock system power unit for supplying a DC tertiary lockcontrol signal to an electromechanical tertiary lock assembly,comprising: a step-down transformer adapted to receive a tertiary lockrelease command signal, the tertiary lock release command signal beingan AC signal of a first peak voltage magnitude, the step-downtransformer operable, upon receipt of the tertiary lock release commandsignal, to supply an AC signal of a second peak voltage magnitude, thesecond peak voltage magnitude being less than the first peak voltagemagnitude; a rectifier circuit coupled to receive the AC signal of thesecond peak voltage magnitude from the step-down transformer andconfigured, upon receipt thereof, to supply a DC signal of a thirdvoltage magnitude; and a voltage limiting circuit coupled to receive theDC signal of the third voltage magnitude from the rectifier circuit andoperable, upon receipt thereof, to supply the DC tertiary lock controlsignal to the electromechanical tertiary lock assembly at a fourthvoltage magnitude, the fourth voltage magnitude less than or equal to apredetermined voltage limit, the voltage limiting circuit comprising: avoltage limiter coupled in parallel with the rectifier circuit andconfigured to limit the DC tertiary lock control signal to the fourthvoltage magnitude, the voltage limiter including a first terminal, asecond terminal, and a third terminal, the first terminal coupled to therectifier circuit, the second terminal coupled to the rectifier circuitand adapted to couple to the electromechanical tertiary lock assembly;and a voltage follower circuit including at least an input terminal, anoutput terminal, and a control terminal, the voltage follower circuitinput terminal coupled to the voltage limiter first terminal, thevoltage follower circuit control terminal coupled to the voltage limiterthird terminal, and the voltage follower circuit output terminal adaptedto couple to the electromechanical tertiary lock assembly; a resistorcircuit and a zener diode circuit electrically coupled in series withone another, the resistor circuit electrically coupled in series betweenthe first and third terminals, and the zener diode circuit electricallycoupled in series between the second and third terminals; and a diodecircuit electrically coupled in series with the resistor circuit and thezener diode circuit.
 2. The power unit of claim 1, wherein the diodecircuit is configured to prevent reverse current flow through the zenerdiode.
 3. The power unit of claim 1, wherein the voltage followercircuit comprises a Darlington pair.
 4. The power unit of claim 1,wherein the step-down transformer includes a primary winding and asecondary winding, and wherein the power unit further comprises: aninput filter circuit coupled to the step-down transformer primarywinding, the filter circuit configured to receive the tertiary lockrelease command signal and remove selected frequency componentstherefrom.
 5. The power unit of claim 1, wherein the rectifier circuitcomprises a full-wave bridge rectifier circuit.